1. Power grid failure
Lightning, destroyed lines, network overload, accidents and natural disasters, for example, lead to network failure.
2. Short-term undervoltage
For example, due to the switching on of large consumers, switching operations in the supply network, failure of network systems, lightning strike or power supply systems that are not able to cope with the requirements. In addition to pure failures, hardware can also be damaged.
3. Short-term overvoltage
Usually caused by lightning and can briefly raise the mains voltage to values of over 6,000 volts. A voltage spike almost always causes data loss or hardware damage.
4. Long-lasting undervoltage
For example, when the line voltage is intentionally lowered to reduce power during peak consumption periods or when the connected load exceeds the supply capacity.
5. Long-lasting overvoltage
Triggered by strong load reduction, disconnection of large consumers and other switching operations in the network. Hardware can be destroyed as a result.
6. Electrical interference signals with higher frequencies
Can be caused by electromagnetic interference (EMI) or radio frequency interference (RFI) from welding equipment, transmitters, printers, thunderstorms, etc.
7. Instability of the mains frequency
E.g. due to load changes on generators, especially smaller ones. Frequency deviations can cause faulty processes, data loss, system breakdowns and damage to equipment.
8. Peaks due to switching operations
Spikes usually lasting in the nanosecond range.
9. Harmonic distortion (harmonics) due to nonlinear load
Switching power supplies, stepper motors, copiers and fax machines, for example, are nonlinear consumer loads. They can cause communication errors, overheating and hardware damage.
As a rule, offline UPS cover points 1-3, line-interactive UPS points 1-5 and (online) double-conversion UPS points 1-9.
Double-conversion UPSs filter the power in any case and ensure consistent power quality throughout. They are therefore the best choice for critical applications.